[evlatests] EVLA performance, 10 Sept

[Rick Perley]

   The usual 'stress test' was done in continuum yesterday (Monday) 
afternoon.  Besides the issues noted yesterday, I find:

    1)  Antennas 11 and 18, on the A and C sides, are showing the 
'square wave' phase jumps, approximately once every 30 seconds or so.  
However, this behavior was seen only at L, C, and X bands.  No jumps 
occurred at K or Q bands. 
   
    2) Antenna 11, of IFs B and D only, at L-band only, shows large 
(20%) amplitude drops on short (< 3 second) timescales.  This doesn't 
appear to be happening at any other band. 

    3) Antenna 14's phase, all IFs, is unstable at L and X bands.  It 
seems o.k. at K and Q bands.  No data at C-band for this antenna (see 
note later). 

    4) A large number of curious flagging issues were found.  I have 
sorted them by band:

    i) L-Band:  21B was flagged, but the data seemed fine -- except that 
the amplitudes were more unstable (varying by about 10%) than the other 
IFs from this antenna.  The flags are probably right! 

    ii) C-Band:  Antennas 11, 13, 14 and 16 gave no fringes (why?) -- 
and were correctly flagged.  Antenna 21A and 19B were both flagged, but 
gave good stable fringes. 

    iii)  X-Band:  There were two scans here.  On the first, antenna 13 
was flagged in all IFs, and 21A was also flagged.  On the second, only 
19A was flagged.  In all cases, the amplitudes and phases appeared 
fine.  *** However -- when the amplitudes were compared to the other 
scan, for which they were not flagged, it was found in all cases that 
the amplitudes were notably different.  Hence, although we had stable 
fringes, the flagger was correct in assigning flags. 

    iv) K-Band:  Antennas 13 and 24, on all IFs, gave no fringes.  Also, 
26A, 17B, and 21B.  In all cases, the data were not flagged. 

    v) Q-Band:   Antennas 13, 17, and 22 gave no fringes on any IF.  
Antenna 24A also gave no fringes.  Of these, 17, 22 and 24 were not 
flagged.